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Design automation and optimization of honeycomb structures for maximum sound transmission loss.

机译：蜂窝结构的设计自动化和优化，可最大程度地降低声音传输损失。

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摘要

Cellular materials with macro effective properties defined by repeated meso-structures are increasingly replacing conventional homogeneous materials due to their high strength to weight ratio, and controllable effective mechanical properties, such as negative Poisson's ratio and tailored orthotropic elastic properties. Honeycomb structures are a well-known cellular material that has been used extensively in aerospace and other industries where the premium on the weight reduction with high-strength is required. Common applications of honeycomb cellular structures are their use as the core material in sandwich plates and plates between two face sheets. Honeycomb structures are built from repetition of a common hexagonal unit cell tessellation defined by four independent geometric parameters; the hexagonal unit cell side lengths, h, and l, cell wall thickness, t and orientation of the angle between the cell walls&thetas;. These parameters can be controlled to achieve desirable effective properties.;Another important application of honeycomb sandwich structures is the ability to adjust the unit cell geometric parameters to increase the Sound Transmission Loss (STL); a metric for measurement of noise cancellation for acoustic waves passing though the panel structure, while maintaining a low mass, and controllable effective stiffness and strength properties. Previous research has been limited to parametric studies exploring the effect of change in a single unit cell parameter on the Sound Transmission Loss (STL). To obtain an optimal STL result and to determine sensitivities, the present work presents a novel technique to control all four of the unit cell parameters while maintaining constant overall dimensions and mass of the honeycomb sandwich plate. These two constraints are necessary to ascertain that the high STL occurs only due to the change in geometric properties of honeycomb unit cell, as the STL increases with increase in mass and change in overall dimensions.;An optimization problem has been set-up with the design variables as hexagonal interior angle, number of unit cells in the horizontal direction, and number of unit cells in the vertical direction for a representative plate model with in-plane acoustic pressure wave transmission analysis. The optimization process required a complete design automation workflow of geometry creation based on changes in number of cells, constraints on overall dimensions and mass, output results extraction, construction of response surface to expedite the optimization using genetic algorithms. The process involved a coupled structural-acoustic finite element model with direct steady-state analysis and natural frequency extraction created and solved using the commercial finite element software package ABAQUS. The model is used to obtain acoustic pressure values for calculation of the STL of the honeycomb sandwich plate. Quadratic Timoshenko beam elements have been used to discretize the thin-walled honeycomb cellular structures for increased accuracy at higher frequencies. The elastic structure model is coupled with acoustic elements by applying surface based tie-constraints to transfer normal plate surface accelerations as input to calculate radiated sound pressure. The entire process of finite element model creation and solution has been parameterized and automated by extensive use of Python scripts directly interfaced with the ABAQUS solver. A detailed workflow has been set-up in the optimization package modeFRONTIER that generates the input variables using a genetic algorithm, NSGA-II, controls the Python scripts to create and solve the finite element Abaqus model, calls the Python scripts to extract results for post-processing needed to generate the STL vs. Frequency plots and finally optimizes the geometric unit cell parameters to maximize STL over a typical frequency range, all while respecting constraints on overall dimensions and mass. The frequency range from 200 Hz to 400 Hz was used to demonstrate the design automation and optimization process developed. The same workflow can be used to optimize STL for other frequency ranges. (Abstract shortened by UMI.).
机译：具有重复有效的介观结构的宏观有效性能的蜂窝材料，由于其高的强度重量比以及可控的有效机械性能（例如负泊松比和定制的正交各向异性弹性性能），正逐渐取代传统的均质材料。蜂窝状结构是一种众所周知的蜂窝状材料，已广泛用于航空航天和其他行业，在这些行业中，需要兼顾轻量化和高强度的要求。蜂窝状蜂窝结构的常见应用是将其用作夹心板和两个面板之间的板的核心材料。蜂窝结构是通过重复由四个独立的几何参数定义的常见六边形晶胞细分来构建的；六边形单元格的边长 h 和 l ，细胞壁厚度， t 以及细胞壁之间的角度方向 ＆thetas; 。可以控制这些参数以获得理想的有效性能。蜂窝夹层结构的另一个重要应用是能够调节晶胞几何参数以增加声传输损耗（STL）。一种测量穿过面板结构的声波的噪声消除的量度，同时保持较低的质量以及可控制的有效刚度和强度特性。以前的研究仅限于参数研究，这些研究探讨了单个晶胞参数的变化对声音传输损耗（STL）的影响。为了获得最佳的STL结果并确定灵敏度，本工作提出了一种新颖的技术，可控制所有四个晶胞参数，同时保持蜂窝状夹心板的整体尺寸和质量恒定。这两个约束对于确定高STL仅由于蜂窝单元格的几何特性的变化而发生是必要的，因为随着质量的增加和整体尺寸的变化STL随之增加。设计变量包括六角形内角，水平方向上的晶胞数量和垂直方向上的晶胞数量，用于具有平面声压波传输分析的代表性板模型。优化过程需要基于单元数量的变化，对整体尺寸和质量的约束，输出结果提取，响应面的构建以完成几何设计的完整设计自动化工作流程，以使用遗传算法加快优化过程。该过程涉及使用直接有限元分析和固有频率提取的结构声学有限元模型，使用商业有限元软件包ABAQUS创建并求解。该模型用于获得声压值，以计算蜂窝夹层板的STL。二次季莫申科梁单元已被用于离散化薄壁蜂窝蜂窝结构，以提高在更高频率下的准确性。通过应用基于表面的约束，将弹性板模型与声学元件耦合，以传递法向板表面加速度作为输入来计算辐射声压。广泛使用直接与ABAQUS求解器连接的Python脚本，对有限元模型创建和解决方案的整个过程进行了参数化和自动化。已在优化包modeFRONTIER中设置了详细的工作流程，该工作流程使用遗传算法NSGA-II生成输入变量，控制Python脚本创建和求解有限元Abaqus模型，调用Python脚本提取结果以供发布生成STL与频率曲线图并最终优化几何单位像元参数以在典型频率范围内最大化STL所需的处理，同时还要考虑到对整体尺寸和质量的约束。 200 Hz至400 Hz的频率范围用于演示开发的设计自动化和优化过程。可以使用相同的工作流程为其他频率范围优化STL。 （摘要由UMI缩短。）。

著录项

  • 作者

    Galgalikar, Rohan Ram.;

  • 作者单位

    Clemson University.;

  • 授予单位 Clemson University.;
  • 学科 Engineering Mechanical.
  • 学位 M.S.
  • 年度 2012
  • 页码 160 p.
  • 总页数 160
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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